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      1 /*	$OpenBSD: ftell.c,v 1.6 2005/08/08 08:05:36 espie Exp $ */
      2 /*-
      3  * Copyright (c) 1990, 1993
      4  *	The Regents of the University of California.  All rights reserved.
      5  *
      6  * This code is derived from software contributed to Berkeley by
      7  * Chris Torek.
      8  *
      9  * Redistribution and use in source and binary forms, with or without
     10  * modification, are permitted provided that the following conditions
     11  * are met:
     12  * 1. Redistributions of source code must retain the above copyright
     13  *    notice, this list of conditions and the following disclaimer.
     14  * 2. Redistributions in binary form must reproduce the above copyright
     15  *    notice, this list of conditions and the following disclaimer in the
     16  *    documentation and/or other materials provided with the distribution.
     17  * 3. Neither the name of the University nor the names of its contributors
     18  *    may be used to endorse or promote products derived from this software
     19  *    without specific prior written permission.
     20  *
     21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     31  * SUCH DAMAGE.
     32  */
     33 
     34 #include <stdio.h>
     35 #include <errno.h>
     36 #include "local.h"
     37 
     38 /*
     39  * ftello: return current offset.
     40  */
     41 off_t
     42 ftello(FILE *fp)
     43 {
     44 	fpos_t pos;
     45 
     46 	if (fp->_seek == NULL) {
     47 		errno = ESPIPE;			/* historic practice */
     48 		pos = -1;
     49                 goto out;
     50 	}
     51 
     52 	/*
     53 	 * Find offset of underlying I/O object, then
     54 	 * adjust for buffered bytes.
     55 	 */
     56         FLOCKFILE(fp);
     57 	__sflush(fp);		/* may adjust seek offset on append stream */
     58 	if (fp->_flags & __SOFF)
     59 		pos = fp->_offset;
     60 	else {
     61 		pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR);
     62 		if (pos == -1)
     63 			goto out;
     64 	}
     65 	if (fp->_flags & __SRD) {
     66 		/*
     67 		 * Reading.  Any unread characters (including
     68 		 * those from ungetc) cause the position to be
     69 		 * smaller than that in the underlying object.
     70 		 */
     71 		pos -= fp->_r;
     72 		if (HASUB(fp))
     73 			pos -= fp->_ur;
     74 	} else if (fp->_flags & __SWR && fp->_p != NULL) {
     75 		/*
     76 		 * Writing.  Any buffered characters cause the
     77 		 * position to be greater than that in the
     78 		 * underlying object.
     79 		 */
     80 		pos += fp->_p - fp->_bf._base;
     81 	}
     82 out:	FUNLOCKFILE(fp);
     83 	return (pos);
     84 }
     85 
     86 /*
     87  * ftell() returns a long and sizeof(off_t) != sizeof(long) on all arches
     88  */
     89 #if defined(__alpha__) && defined(__indr_reference)
     90 __indr_reference(ftello, ftell);
     91 #else
     92 long
     93 ftell(FILE *fp)
     94 {
     95 	long pos;
     96 
     97 	pos = (long)ftello(fp);
     98 	return(pos);
     99 }
    100 #endif
    101